180 degrees rule

The 180 degrees rule is a basic guideline the demonstrates on-screen spatial relationship between a character and another character or object within a scene. An imaginary line called the axis connects the characters and by keeping the camera on one side of this axis for every shot in the scene, the first character will always be seen right of the second character, who is then always seen left of the first. If the camera passes over the axis, it is called crossing on the line or jumping on the line.